Palatal incompetency appears to stimulate compensatory behaviors which tend to undermine rather than enhance speech performance. Recent studies in our laboratory suggest that these behaviors may be attempts to satisfy the requirements of a pressure regulating system. The objective of this research is to determine whether the compensatory responses associated with cleft palate are strategies devised to regulate speech pressures and control airflow and airway resistance. The purpose of a regulating system is to maintain a parameters constancy. The control process is the means by which this is accomplished. We propose that control of structural movements (resulting upper airway resistance) and airflow is necessary for regulation of speech pressures. Study of a regulating system involves experiments which identify and describe mechanisms of control. The use of subjects with different degrees of palatal incompetency will allow us to assess how the system is managed when an error is introduced. The pressure-flow technique, developed in our laboratory, will be used to measure respiratory parameters associated with speech and assess structural responses. The following questions will be addressed: I. Are intraoral speech pressures maintained at appropriate magnitudes across subjects and conditions of velopharyngeal competency? II. Does the significant increase in volume rate of airflow and effort in cleft palate speech correlate with the maintenance of pressure for consonant productions? III. Do the structures of the oral and nasal cavities interact in a complementary fashion that maintains pressure and controls airflow? IV. Are upper airway resistances controlled during speech in a manner characteristic of a pressure regulating system? and V. Are changes in timing patterns associated with velopharyngeal incompetency consistent with the characteristics of a regulating mechanism? If we determine that attempts to achieve an aerodynamic constancy result in compensatory responses, then new explanations for cleft palate speech should follow and new approaches to treatment would be possible.